National security and emergency preparedness (NS/EP) personnel have become dependent on commercial wireless communications for the performance of their mission. NS/EP personnel frequently require wireless connectivity in order to provide communications in a mobile environment when responding to emergencies such as earthquakes, hurricanes, and floods. Commercial wireless service provides a cost-effective capability for NS/EP communications that leverages the use of publicly available wireless telephony rather than a cost-prohibitive private network. In addition to minimizing costs and deployment time, this arrangement provides broad accessibility.
However, following a disaster, severe cellular network congestion in any surviving telecommunication systems can cause high call blocking in wireless communications. Thus a priority access service (PAS) has been deemed necessary to enable critical disaster relief officials to provide services when they are most needed. A wireline PAS currently exists, the Government Emergency Telecommunications Service (GETS) program, but a wireless capability is still lacking. Even in non-disaster situations, a high volume of call traffic can create congestion in cellular networks, leading to a need for redistribution of the cell load.
The US National Communications System (NCS) was chartered to work with cellular and personal communications services (PCS) operators and vendors to provide wireless PAS for NS/EP personnel during emergency situations. The PAS program has been implemented through a series of Federal Communications Commission (FCC) rules and orders that establish the regulatory, administrative, and operational framework that enables commercial mobile radio service (CMRS) providers to offer PAS to NS/EP personnel. CMRS providers include cellular licensees, broadband personal communications service (PCS) licensees, and specialized mobile radio (SMR) licensees.
The initial operating capability (IOC) for PAS is to provide “radio” priority access for Code Division Multiple Access and Global System for Mobile Communication (GSM) air interfaces by Dec. 31, 2002, i.e., PAS originating calls have a higher priority for access to next available radio resource than public (non-priority) calls. (See NS/EP Wireless Priority Service (WPS) Industry Requirements Document for the Initial Operating Capability (IOC) for CDMA-based Systems, Issue: 1.0, Feb. 22, 2002; and NS/EP Wireless Priority Service (WPS) Industry Requirements Document for the Initial Operating Capability (IOC) for GSM-based Systems, Issue: 1.0, Feb. 22, 2002.) The full operating capability (FOC) is to provide end-to-end priority access by Dec. 31, 2003. The basic mechanism proposed is to queue priority call requests when there are no radio channels available. As radio channel becomes available, preference will be given to queued priority calls. In the current implementation of IS-95/cdma2000 CDMA base station (BS) and base station controller (BSC), there is no call queuing capability. As a result, priority queues are required to be added to the BS/BSC. GSM base station sub-system (BSS) already has the call queuing capability. As a result, minimal change is required for the GSM BSS to support PAS. PAS is activated on a per call basis and is applicable to mobile-to-wireline, wireline-to-mobile and mobile-to-mobile links. When an NS/EP user places a PAS call and the service is activated, the mobile station (MS) requests a voice channel via the control channel messaging. In a congested environment, the NS/EP caller is placed in a queue and will be given the next available voice channel. PAS does not preempt calls in progress and is to be used only in emergency situations where network congestion is blocking call attempts, however the invention as described below is not limited in this regard.
Another task of the FCC is enforcement of the Wireless Communications and Public Safety Act of 1999 (the “911 Act”), which mandates the FCC to promote “safety of life and property through the use of wire and radio communication.” To this end, the FCC has adopted requirements that cellular, broadband PCS, and certain Specialized Mobile Radio (SMR) licensees implement 911 and E911 services. One of the requirements is that wireless carriers and cell phone manufacturers provide the capability not just to deliver 911 calls to emergency dispatchers, or Public Safety Answering Points (PSAPs), but also to automatically identify to the PSAPs the location from which a wireless call is being made. The 911 Act's requirements were divided into two phases. Phase I required wireless carriers to deliver the telephone number of the handset originating an E911 call, and the location of the cell site or base station receiving the E911 call, to the PSAPs. Phase II requires carriers to deliver more specific latitude and longitude location information, known as Automatic Location Identification (ALI) to the PSAPs. Full implementation of this phase is expected by the end of 2005, but by Dec. 31, 2002, all new digital handsets are to be activated by wireless carriers are to be ALI-capable.
A variety of techniques (e.g., GPS, Angle of Arrival, Time Difference of Arrival, and others) are currently being used to implement ALI capabilities. U.S. Pat. Nos. 5,388,147 and 5,479,482 to Grimes teach combining a cellular telephone and a GPS receiver so that the phone's approximate physical location, i.e., its approximate geocoordinates, can be reported as part of the emergency call. Alternatives to GPS exist, but every technique for enabling ALI results from measuring the cellular device's position by reference to established points whose positions are known. The cellular device's location is estimated to lie at the best intersections (in a least-squares or maximum likelihood sense, since all location measurements have random errors) of curves whose shapes and locations are determined by the particular technique utilized.
Thus, a need exists for assisting NS/EP personnel in acquiring PAS. A system that accomplishes this objective by leveraging existing technological architectures would be quite useful.
Additionally, cell congestion causes blocking problems for the general population of wireless subscribers. What is needed is a way for any user of a mobile wireless system to acquire access to cellular services when the cell in which the user is currently located is congested. Such a system may serve to alleviate cell congestion by redistribution of cell loading to less congested cells.